Absorption refrigeration and related apparatus employing a composite refrigerant fluid and a refrigeration loop is well known. The refrigeration loop includes a generator, a condenser, an evaporator, and an absorber. A variety of composite refrigerant fluids can be used in such apparatus. Two examples are an ammonia/water system and a lithium bromide/water system.
Heat from a source of energy outside the refrigeration loop is added to the composite refrigerant in the generator. The generator heats the composite liquid refrigerant sufficiently to distill out a vapor of the more volatile component or phase of the refrigerant (for example, ammonia vapor in the case of the ammonia/water refrigerant and water in the case of the lithium bromide/water system), leaving a less-volatile component or phase of the refrigerant behind. The less-volatile refrigerant component can either be more concentrated than the composite refrigerant (as when water vapor is distilled out of an aqueous lithium bromide solution) or more dilute than the initial refrigerant (as when ammonia is driven out of water solution). The remaining less-volatile refrigerant component is removed to the absorber.
The condenser receives the vapor phase of the refrigerant from the generator and condenses it to liquid form (also known as a condensate). The heat released by the condensation of the vapor is rejected to a cooling tower, cooling water, some other external heat sink, or another stage of the refrigeration apparatus.
The evaporator withdraws heat from a heat load (i.e. the building air, refrigerator contents, cooling water, or other medium the system is designed to cool) by evaporating the condensed liquid refrigerant in direct or indirect contact with the heat load. The evaporator thus revaporizes the volatile refrigerant component.
The absorber contacts the refrigerant vapor component leaving the evaporator with the less-volatile refrigerant component leaving the generator. The contacting process generates heat when the vapor phase is reabsorbed in the less-volatile refrigerant phase. This heat is rejected to a cooling tower, cooling water, another stage of the refrigeration apparatus, or some heat sink. The original composite refrigerant is reformed in the absorber, and then is returned to the generator to complete the cycle.
Triple-effect refrigeration apparatus has two separate but interacting refrigeration circuits of the type described above (sometimes respectively known as a high-temperature loop and a lower temperature loop, as a high loop and a low loop, or as a first loop and a second loop). The first and second loops are interconnected so heat is transferred from the absorber and the condenser of the first loop to the generator of the second loop. Both the first loop and the second loop accept heat from the heat load. The second loop rejects heat from its absorber and its condenser to an external heat sink.
One known generator, which uses steam as a heat source, comprises an outer vessel which is closed at each end and inner vessels which are vertical tubes passing through the outer vessel. Heat supplied to the outer vessel in the form of steam from a source outside the refrigerant loop heats the tubes, and thus the refrigerant within the tubes. The refrigerant is boiled within the tubes, and the vapor and entrained liquid is conveyed upwardly and expelled from the upper ends of the tubes.
An absorber is known in which the less-volatile component of the refrigerant trickles down from coil to coil on the substantially horizontal coils of a heat exchanger as it absorbs the refrigerant vapor leaving the evaporator. The heat exchanger removes the heat resulting from the absorption process. The heat is rejected to a heat sink, such as cooling water.
Certain absorption additives, when present in a refrigerant fluid in the absorber, increase the efficiency of absorption refrigeration systems. These additives function by increasing the rate of absorption of one component of the refrigerant in the other component of the refrigerant.
Generally, these absorption additives are volatile when exposed to the temperatures and pressures such as would be found in the generator, evaporator or condenser of a typical absorption refrigeration system. In addition, they are nearly insoluble in the bulk refrigerant fluid, so that when present in practical concentrations they exist mostly in an immiscible, second liquid phase. In such a system, the additive, although less volatile then the more volatile component (e.g., water in Lithium Bromide--water systems, or ammonia in ammonia water systems) of the refrigerant system, can be separated at relatively low temperatures by steam distillation.